Method and apparatus for testing vehicle exhaust emissions

ABSTRACT

This invention provides a method and apparatus for testing exhaust emissions of vehicles having internal combustion engines. The apparatus of the present invention comprises a test track over which a vehicle is moved under its own power and remote exhaust testers which spectroscopically test exhaust emissions of vehicles as they move over the test track. The apparatus and method of the present invention preferably may be used for pre-screening vehicles as a first step in a testing process utilizing, as a second step, more extensive testing as with stationary testing apparatus. Those vehicles clearly meeting minimum emissions standards can be relatively quickly screened out by the method and apparatus of the present invention and exempted from further, more extensive testing.

FIELD OF THE INVENTION

This invention relates to testing exhaust emissions of vehicles havinginternal combustion engines.

BACKGROUND OF THE INVENTION

Due to mounting concerns over air quality, numerous jurisdictions inNorth America, Europe and Asia have instituted mandatory testingprograms wherein exhaust emissions of vehicles are tested to determinewhether they meet minimum standards set by a government agency.Typically, this testing of exhaust emissions is conducted annually andis a necessary precondition to renewal of vehicle registration. UnitedStates government standards for volatile organic compounds, oxides ofnitrogen and carbon monoxide as defined by the U.S. EnvironmentalProtection Agency are contained in the Federal Register, Part 51.

It has been found that most vehicles meet emissions standards. Mostvehicle-related air pollution is caused by a relatively small proportionof vehicles, many of which have emission control systems which aremalfunctioning or have been tampered with.

Presently used tests to accurately determine emission levels and todiagnose problems with vehicle emission controls are time consuming.Typically, vehicles must be brought to a central testing facility, andtested on a stationary testing apparatus by direct sampling of theexhaust.

The disadvantage exists that widespread testing of vehicles usingstationary testing apparatus is very time consuming. This results inundue hardship for motorists, who must endure long lineups at testingfacilities.

Another disadvantage exists that stationary testing apparatus is veryexpensive, and therefore the cost of testing a vehicle on stationaryapparatus is relatively high.

There are also presently available remote sensing testing apparatuswhich quickly test exhaust emissions by spectroscopic methods, which maygenerally be defined as methods which detect the presence of a substanceby measurement of the radiant energy absorbed or emitted by thesubstance in any of the wavelengths of the electromagnetic spectrum. Forexample, presently available remote sensing testing apparatus typicallytest exhaust emissions by the use of ultrasensitive infrared detectiontechnology. Remote sensing testing apparatus utilizing ultrasensitiveinfrared detection technology typically operates by passing a choppedinfrared beam through the exhaust plume of a vehicle in close proximityto the exhaust pipe of the vehicle. The absorption intensity of the beamis measured after it is passed through the exhaust plume and the levelsof certain target compounds present in the exhaust emissions of thevehicle are then calculated.

In conclusion, the disadvantage exists that accurate testing of vehicleemissions using stationary testing apparatus is time consuming andexpensive. Although quicker and cheaper, remote sensing testing istypically less accurate than stationary testing in estimating levels ofvehicle emissions.

SUMMARY OF THE INVENTION

The present invention at least partially overcomes these disadvantagesby providing an apparatus and a method for testing vehicles which issubstantially faster and cheaper than stationary testing apparatus, andprovides substantially greater precision than roadside remote sensingtesting apparatus.

The apparatus of the present invention comprises a test track over whicha vehicle is moved under its own power. The apparatus includes remotesensing exhaust testers positioned along the track to test the exhaustemissions of vehicles as they are driven along the track. The exhaustemissions of the vehicles are preferably tested under at least twodifferent modes of operation to provide a reliable indication of exhaustemissions.

The apparatus and method of the present invention preferably may be usedfor pre-screening vehicles as a first step in a testing processutilizing, as a second step, more extensive testing as with stationarytesting apparatus. Those vehicles, typically comprising a significantportion of vehicles being pre-screened, which clearly meet minimumemission standards, can be relatively quickly screened out and exemptedfrom further testing. The vehicles which do not clearly meet minimumemission standards are then subjected to more extensive testing, as forexample, by being tested and diagnosed on a stationary testingapparatus.

Therefore, the method and apparatus of the present invention can be usedto eliminate the need for stationary testing of a significant portion ofvehicles. By quickly and effectively identifying polluting vehicles, thepresent invention substantially increases the speed of vehicle emissiontesting without sacrificing accuracy in the measurement of emissionlevels.

It is one object of the present invention to provide an improvedapparatus and method for testing exhaust emissions of internalcombustion vehicles.

It is a further object of the present invention to provide apre-screening system to quickly identify and separate vehicles whichclearly meet emission standards from those which do not or may not.

In one aspect, the present invention comprises a method of testingexhaust emissions of vehicles having internal combustion engines toestimate whether the emissions of any vehicle meet predeterminedstandards, comprising: moving each vehicle under its own power along atest track under controlled conditions of operation, the test trackhaving an upwardly inclined portion, a horizontal portion and adownwardly inclined portion, the method comprising the steps of: movingthe vehicle to ascend the upwardly inclined portion at a positive rateof acceleration and within a first range of velocities, and remotelytesting the exhaust emissions of the vehicles by spectroscopic means asthe vehicle ascends the upwardly inclined portion at a first test pointon the upwardly inclined portion; moving the vehicle across thehorizontal portion at a substantially constant velocity and within asecond range of velocities, and remotely testing the exhaust emissionsof the vehicle by spectroscopic means as the vehicle crosses thehorizontal portion at a second test point on the horizontal portion; andmoving the vehicle to descend the downwardly inclined portion at anegative rate of acceleration and within a third range of velocities,and remotely testing the exhaust emissions of the vehicle byspectroscopic means as the vehicle descends the downwardly inclinedportion at a third test point on the downwardly inclined portion;comparing the test results from the first, second and third test pointsof one vehicle with results for vehicles which meet the predeterminedstandards, said steps being performed in any order.

In another aspect, the present invention provides an apparatus fortesting exhaust emissions of vehicles having internal combustionengines, comprising: a test track over which vehicles are moved undertheir own power under controlled conditions of operation, the test trackhaving an upwardly inclined portion, a horizontal portion and adownwardly inclined portion; a first remote sensing tester for testingthe exhaust emissions of the vehicles by spectroscopic means, the firsttester located at a first test point on the upwardly inclined portion; asecond remote sensing tester for testing the exhaust emissions of thevehicles by spectroscopic means, the second tester located at a secondtest point on the second horizontal portion; a third remote tester fortesting the exhaust emissions of the vehicles by spectroscopic means,the third tester located at a third test point on the third inclinedportion; and a processor for comparing the test results from the first,second and third test points of one vehicle with results for vehicleswhich meet the predetermined standards.

Preferably, a stream of air is directed at the track by a blower locatedahead of a test point, vehicles passing through the air stream beforemoving past the test point, the air stream clearing from the trackexhaust emissions carried along the track by a vehicle as the vehiclepasses through the air stream, the exhaust emissions tested at the testpoint substantially comprising only an exhaust plume emitted by theexhaust pipe of the vehicle between the air stream and the test point.

More preferably, a stream of air is directed at the track ahead of eachtest point.

Preferably, the remote testers comprise a source of infrared radiationand a detector of infrared radiation, the source emitting a beam ofinfrared radiation which passes through an exhaust plume of a vehicleand is subsequently detected by the receiver, the exhaust plume locatedat the test point and in close proximity to the exhaust pipe of avehicle.

In yet another aspect, the present invention provides a method oftesting exhaust emissions of vehicles having internal combustionengines, comprising: a first pre-screening step, comprising testingvehicles according to the method and apparatus of the present inventiondescribed above to estimate whether the emissions of any vehicle meetpredetermined standards; and a second step comprising testing exhaustemissions to accurately determine whether the emissions of any vehiclemeet predetermined standards, the second step not being conducted forvehicles likely to have emissions meeting the predetermined standard, asestimated by the pre-screening step.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will be apparentfrom the following description, taken together with the accompanyingdrawings in which:

FIG. 1 schematically illustrates a testing apparatus according to afirst preferred embodiment of the present invention;

FIG. 2 schematically illustrates a preferred method for testing theexhaust of a vehicle according to the present invention;

FIG. 3 is a plot of velocity in feet per second versus distance in feetshowing preferred conditions for velocity and acceleration in apreferred testing method of the present invention utilizing theapparatus shown in FIG. 1;

FIG. 4 is a plot of velocity in feet per second versus time in secondsfor the velocity and acceleration conditions shown in FIG. 2; and

FIG. 5 illustrates a testing apparatus according to a second preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred testing apparatus according to the present inventionis shown in FIG. 1.

The preferred apparatus 10 is shown in FIG. 1 as comprising a test track12, three remote sensing exhaust testers 14, each comprising a source 16and a detector 18 located on opposite sides of track 12, and threeblowers 20.

FIG. 1 illustrates the test track 12 as comprising three portions; afirst, upwardly inclined portion 22, a second, flat, horizontal portion24, and a third, downwardly inclined portion 26.

Vehicle 28 is moved over track 12 under its own power, first ascendingalong first inclined portion 22, then moving horizontally alonghorizontal portion 24, and lastly descending along second inclinedportion 26.

Vehicle 28 is moved over track 12 under controlled conditions ofacceleration and velocity. Preferably, vehicle 28 starts from a stop atthe bottom of first inclined portion 22 and ascends along inclinedportion 22 at a constant, positive, rate of acceleration, moves acrosssecond horizontal portion 24 with constant velocity, and then descendsalong the third inclined portion 26 at a constant, negative rate ofacceleration.

The exhaust emissions of vehicle 28 are tested at three test points 30,32 and 34 located along the track 12.

The test points 30, 32 and 34 are illustrated in FIG. 1 as planesthrough which vehicle 28 passes as it moves along test track 12.

First test point 30 is located proximate the upper end of the firstinclined portion 22. At the first test point 30, the vehicle 28 ispreferably accelerating at a constant rate up inclined portion 22.

The second test point 32 is located on the second horizontal portion 24,preferably about two thirds of the distance along portion 24. At thesecond test point 32 the vehicle 28 is preferably moving at constantvelocity along central portion 24.

The third test point 34 is located on the third inclined portion 26proximate its upper end. At the third test point 34, the exhaustemissions of vehicle 28 are tested as it descends along third inclinedportion 26, preferably at a constant negative rate of acceleration.

The inventor has determined that the testing of exhaust emissions at thepreferred locations of test points 30, 32 and 34 along test track 12provides a good approximation of exhaust emissions of vehicle 28.

FIG. 2 illustrates a preferred manner in which the exhaust emissions ofvehicle 28 are tested at one test point along a test track 12.

FIG. 2 illustrates vehicle 28 having a conventional exhaust pipe 36located at the rear of and underneath vehicle 28. Exhaust pipe 36 formsthe terminal end of an exhaust system (not shown) through which exhaustemissions produced by the internal combustion engine powering vehicle 28are released into the environment.

The exhaust emissions are released from exhaust pipe 36 in the form ofan exhaust plume 38, which is a cloud of exhaust matter extendingrearwardly from exhaust pipe 36 and located above the surface of testtrack 12. Typically, the most dense area of exhaust plume 38 is about 8inches in diameter and is centred about 14 to 16 inches above track 12,depending on the height of exhaust pipe 36.

FIG. 2 illustrates the exhaust plume 38 being tested at test point 40,shown as a plane, by remote sensing exhaust tester 41.

The exhaust plume 38 is preferably tested in close proximity to the endof exhaust pipe 36. Therefore, a sensor is preferably provided alongtrack 12 to sense the passing of vehicle 28 through test point 40 andtrigger the exhaust tester 41 to test the exhaust plume 38 of vehicle 28as the exhaust plume 38 passes through test point 40. The sensor fordetecting the passing of vehicle 28 may preferably form an integral partof remote sensing tester 41.

One particularly preferred sensor/trigger mechanism passes a beam acrosstrack 12 transverse to the direction of travel of vehicle 12 at testpoint 40. When the front of vehicle 28 breaks the sensor's beam, thesensor recognizes that the vehicle 28 is passing in front of the sensor.After the rear of vehicle passes through the beam, the beam passesacross the track 12 uninterrupted. The sensor then triggers the remotesensing tester to test the exhaust emissions of vehicle 28 proximateexhaust pipe 36. Preferably, there is a short time delay between theinstant the vehicle 28 finishes passing through the beam and thetriggering of the remote sensing tester to allow plume 38, locatedrearwardly of vehicle 28, to move to test point 40.

The remote sensing exhaust tester 41 comprises a source ofelectromagnetic radiation 16 and a detector 18 which detectselectromagnetic radiation emitted by source 16.

Electromagnetic radiation may be defined as radiant energy in the formof electromagnetic waves, or light. The various forms of electromagneticradiation comprising the electromagnetic spectrum are characterized bytheir wavelengths, and include cosmic rays, gamma rays, x-rays, UV rays,visible light rays, infrared, microwave and radiofrequency rays.Preferably, the electromagnetic radiation emitted by source 16 andreceived by detector 18 comprises UV or infrared, more preferablyinfrared of one or more wavelengths. Although UV and infrared arepreferred in the method and apparatus of the present invention, it is tobe understood that electromagnetic radiation of other wavelengths mayalso be suitable.

Most preferably, source 16 emits a beam 42 comprising infrared radiationof at least one wavelength, each wavelength interacting with a targetcompound present in the exhaust emissions of vehicle 28.

The beam 42 of infrared radiation emitted by source 16 is directedtransversely across track 12 in the plane of test point 40.

FIG. 2 illustrates a particularly preferred tester 41 wherein the source16 and detector 18 are located on the same side of track 12. The beampasses from source 16, through exhaust plume 38, to a reflector 19 onthe opposite side of track 12. Reflector 19 reflects the beam back todetector 18, through exhaust plume 38.

The path length travelled by the beam is preferably about 25 feet, whichis preferably about twice the width of track 12. Therefore, theconfiguration of tester 41 shown in FIG. 2 is preferably used when it isdesired to locate tester 41 directly alongside track 12. However, it isto be understood that locating source 16 and detector 18 on oppositesides of track 12, as shown in FIG. 1, may be equally suitable.

The absorption intensity of the infrared radiation received by detector18 is compared with the intensity of the infrared radiation emitted bysource 16 to provide a measurement representative of the quantity of oneor more target compounds in the exhaust plume 38 of vehicle 28.

The beam 42 emitted by source 16 preferably passes through the centre ofexhaust plume 38, and in close proximity to the end of exhaust pipe 36.For vehicles such as vehicle 28 shown in FIG. 2 having an exhaust pipe36 slightly above track 14, the height of beam 42 is preferably about 12to about 20 inches above the level of track 12, more preferably about 14to about 16 inches above track 12.

The acceleration and velocity of vehicle 28 are preferably monitored asit passes over track 12 to determine whether the motion of vehicle 28 iswithin predetermined parameters of velocity and acceleration. Onepreferred monitoring device is a piezoelectric strip 43 attached totrack 12. The strip 43 can be used to determine the velocity of vehicle28 by measuring the time taken for one tire to move over strip 43. Theacceleration can be determined by measuring the relative velocities ofone front tire and one rear tire of vehicle 12 over strip 43.

Although FIGS. 1 and 2 show only one piezoelectric strip 43, it is to beunderstood that any number of strips 43 may be positioned along track12, and that strips 43 may be positioned at any desired interval, forexample every 5 feet. Although not shown in FIG. 5 for convenience, itis to be understood that strips 43 are also preferably positioned alongtrack 50 of FIG. 5.

The reliability of the test results is at least partially dependent onthe quality of the exhaust plume 38 emitted by vehicle 28. Environmentalfactors such as wind and rain tend to disperse the plume 38, causingunreliable test results. Therefore, the test track 12 is preferablysheltered from wind and precipitation, preferably within a building orshelter.

Water may also be brought onto test track 12 by the vehicles beingtested. For example, water entrained in tire treads or ice and snowattached to the chassis of a vehicle may be deposited on track 12. Thiswater wets track 12 and may be sprayed upwardly by the wheels ofvehicles as they move over track 12 placing water into the path of theemitted beam 42 from the tester 41 and possibly affecting the testresults. This problem can be reduced by shaping track 12 so that waterdeposited on track 12 drains to the centre of track 12 and away from thepaths of vehicle wheels. Preferably, as shown in FIG. 2, track 12 has aslightly V-shaped transverse cross-section and is provided with drains44 at its centre so that water collecting in the centre of track 12 canbe drained away.

The inventor has also found that exhaust fumes collect under vehicle 28and are entrained by vehicle 28 as it moves along track 12. If theseentrained exhaust fumes are present when vehicle 28 passes test point40, less accurate test results will be obtained since the exhaust fumesentrained by vehicle 28 will mix with the exhaust plume 38 being testedat test point 40. The entrained exhaust fumes may contain exhaustemissions emitted under different conditions than at the test point 40and which may not be generally representative of the exhaust emissionsof vehicle 28 at test point 40.

Therefore, as shown in FIG. 2, blowers 20 are preferably positionedproximate track 12 to blow an air curtain 45 onto track 12. The blower20 preferably blows air substantially vertically downward onto track 12and also substantially transverse to track 12. Preferably, the air flowis directed slightly rearwardly relative to the direction of travel of avehicle 28. The blower 20 is preferably positioned so that air curtain45 can "break" exhaust plume 38 shortly before vehicle 28 passes testpoint 40. The inventor has found that directing air flow slightlyrearwardly more efficiently breaks the plume as vehicle 28 moves past ablower 20.

The distance between air curtain 45 and test point 40 must be carefullycontrolled so that the exhaust plume 38 has sufficient time tore-establish itself between air curtain 45 and test point 40. Thepreferred distance between air curtain 45 and test point 40 is dependenton the velocity and acceleration of vehicle 28.

Thus, when vehicle 28 passes through test point 40, substantially theonly exhaust present will be that released from exhaust pipe 36 in theform of exhaust plume 38, the exhaust plume 38 forming between aircurtain 45 and test point 40.

Preferably, a blower 20 is located along track 12 ahead of each testpoint on the test track 12. Although not shown in FIG. 1, a blower 20 ispreferably located ahead of each test point 30, 32 and 34 in order tobreak the exhaust plume of vehicle 28, while being located a sufficientdistance from the test point to allow the exhaust plume of vehicle 28 toreestablish itself for testing at each test point 30, 32 and 34.

As shown in FIG. 2, blower 20 preferably comprises two vertical pipes 15and a horizontal pipe 17 each provided with a row of holes 21, the holes21 being directed downwardly toward track 12 by horizontal pipe 17 andtransversely across track 12 by vertical pipes 15. A source of air (notshown) supplies pressurized air to blower 20. As shown in FIG. 2, blower20 may preferably be supported on legs 23.

It is preferred that vehicle 28 be tested under at least two differentmodes of operation, defined by one or more of velocity, acceleration,engine speed and the ratio of air to hydrocarbon fuel being consumed.These factors have an impact on the composition of the exhaustemissions.

The vehicle 28 preferably moves up first inclined portion 22 in a"loaded" mode. In loaded mode, the vehicle is preferably accelerating upinclined portion 22, more preferably at a constant rate. To achieveloaded mode, vehicle 28 is preferably stopped at the bottom of firstinclined portion 22 before beginning its ascent along inclined portion22. In the loaded mode, because the accelerator pedal is depressed bythe driver, the engine speed is moderately high, preferably about 2,000rpm, and the air:fuel ratio is moderately enriched, preferably in therange of from about 14.7:1, the stoichiometric ratio for ordinarygasolines, to about 13.5:1. It is to be understood that loaded modediffers from "enriched" mode, wherein the accelerator pedal issubstantially fully depressed and the air:fuel ratio is enriched tobelow about 13.5:1.

The vehicle 28 preferably moves across horizontal portion 24 in "cruise"mode, wherein vehicle 28 is moving with substantially constant velocity.In cruise mode, the accelerator pedal is partially depressed, preferablyless than in loaded mode, and therefore the engine speed in cruise modeis less than that in loaded mode, preferably from about 800 rpm to about1500 rpm. The air:fuel ratio in cruise mode is leaner than that inloaded mode, preferably from about 14.0:1 to about 15.0:1.

On second inclined portion 26, vehicle 28 is in "deceleration" mode, andis preferably decelerated by engine braking along at least a portion ofsecond inclined portion 26. In deceleration mode, the acceleration pedalis not depressed, the engine speed is preferably less than that incruise mode and the air:fuel ratio is preferably leaner than that incruise mode.

It is to be understood that the above engine speeds and air:fuel ratiosare only rough estimates and that the engine speeds and air:fuel ratiosdiscussed above would not be applicable to all vehicles.

The test track 12 shown in FIG. 1 may have any suitable dimensions. Theinclined portions 22 and 26 may have different dimensions and slopes,although they are shown in FIG. 1 as preferably having substantially thesame dimensions. Preferably, an angle of incline I measured betweenreference plane G defined by the base of track 12 and the upper surface46 of first inclined portion 22 and between reference plane G and theupper surface 48 of second inclined portion 26 is from about 2° to about10°. Most preferably, the angle of incline I of the inclined portions 22and 26 is about 6°.

The lengths of inclined portions 22 and 26, as measured along referenceplane G, are respectively designated L1 and L3 in FIG. 1.

Preferably, the length L1 of inclined portion 22 is long enough toattain loaded mode and the length L3 of the inclined portion 26 is longenough to attain deceleration mode. More preferably, L1 and L3 are fromabout 30 to about 100 feet. Most preferably, the lengths L1 and L3 areabout 63 feet.

The inclined portions 22 and 26 preferably have the same height H, whichis defined as the maximum vertical rise of the inclined portions 22 and26 above reference plane G. Preferably, height H is from about 2 toabout 8 feet. Most preferably, height H is about 4 feet.

The length L2 of the horizontal portion 24 is long enough for vehicle 28to change from loaded mode to cruise mode. Length L2 is preferably fromabout 40 to about 200 feet, more preferably about 89 feet.

The preferred test track 12 illustrated by FIG. 1 is elevated abovereference plane G. However, it is to be appreciated that test track 12may have numerous configurations. Firstly, test track 12 may compriseone or more inclined portions, with the preferred number of inclinedportions being two, as shown in FIG. 1, and the test track may comprisemore than one flat, horizontal portion. Secondly, the test track 12 isnot necessarily raised above ground level, but may also be partially orwholly situated at or below ground level.

With reference to the preferred apparatus shown in FIG. 1, FIGS. 3 and 4are plots of velocity versus time and velocity versus distance,respectively, illustrating preferred conditions of velocity andacceleration under which vehicle 28 is driven over a particularlypreferred test track 12, having angle I of 6°, H of 4 feet, L1 and L3both 63 feet and L2 of 89 feet.

FIGS. 3 and 4 show that the velocity of vehicle 28 in loaded modepreferably increases at a constant rate of 3 mph/sec (4.4 ft/sec²) as itis driven over upwardly inclined portion 22. At the upper end ofinclined portion 22, vehicle 28 reaches a maximum velocity of 23.5ft/sec, this velocity being reasonably constant as vehicle 28 passesover horizontal portion 24 in cruise mode. When the vehicle 28 reachesdownwardly inclined portion 26, it is preferably decelerated at aconstant rate of 3 mph/sec.

The inventor has found that the first test point 30 is most preferablylocated at a distance of about 50 feet from the lower end of inclinedportion 22, the second test point 32 is most preferably located about 72feet from the beginning of horizontal portion 24, and third test point34 is preferably located about 14 feet from the upper end of inclinedportion 26. Regarding third test point 34, the inventor has found thatthe vehicle 28 is preferably tested after the vehicle has attaineddeceleration mode and after engine braking has begun.

Remote sensing exhaust testers 14 and 41 such as those described abovein reference to FIGS. 1 and 2 are commercially available. Oneparticularly preferred remote sensing exhaust tester is the RES-100 unitof the Santa Barbara Research Center, a subsidiary of Hughes AircraftCompany, sold under the trade mark "SMOG DOG". Remote sensing exhausttesters typically operate by measuring selective absorption of infraredradiation by one or more of carbon monoxide, carbon dioxide,hydrocarbons, nitrogen oxides NO_(x), wherein X is 1/2 to 3, and oxygen,some or all of which may be present in exhaust of vehicles havinginternal combustion engines.

The apparatus of the present invention is preferably initiallycalibrated so that it provides test results reasonably consistent withtest results provided by means which are known to be accurate, such asstationary testing apparatus.

The calibration process preferably comprises testing exhaust emissionsof vehicles using the method of the invention, and comparing the testresults obtained according to the present invention with test resultsobtained by other methods known to be accurate. A correlation isdetermined between the test results obtained according to the presentinvention and the exhaust emissions accurately determined by othermethods.

Using the correlation, it can be determined, with varying levels ofprobability, whether any vehicle tested according to the presentinvention will meet predetermined standard levels of emissions, forexample as prescribed by a government agency.

To improve the correlation between the test results according to thepresent invention and the levels of exhaust emissions accuratelydetermined by other methods, the rate of acceleration and the velocityof each vehicle are preferably carefully controlled as the vehiclepasses each test point along the test track.

Therefore, it is most preferred that the vehicles be driven over thetrack by experienced test drivers capable of keeping velocity andacceleration within preset parameters. However, it is to be appreciatedthat the apparatus of the present invention can be calibrated to allowvehicle owners to drive their own vehicles over the test track. However,the test results would likely be more accurate when the vehicles aredriven by skilled drivers.

When used as a pre-screening step, the method of the present inventionis preferably used to identify vehicles whose emissions with a very highlevel of certainty, meet standards more strict than the predeterminedstandard.

For pre-screening, it is not necessary that the method of the presentinvention identify a high percentage of vehicles whose emissions meetthe predetermined standard, only that at least some of these vehiclesare identified and exempted from further, more extensive, testing.Reducing the number of vehicles subjected to extensive testing wouldattain at least one of the objects of the present invention.

If the most preferred dimensions of the track 12 shown in FIG. 1 areused, with L1 and L3 equal to 63 feet and L2 equal to 89 feet, the totallength of test track 12 will be 215 feet. Although the test track 12 isof a simple design, it would require a relatively large amount of space.

FIG. 5 illustrates a second preferred test track 50 according to thepresent invention. Test track 50 is a four cornered loop having fourstraight sides, all sides having the same length. The preferred lengthof the sides is from about 20 to about 60 feet, with about 40 to about50 feet being most preferred. This track is preferable over that shownin FIG. 1 when space is limited.

The first side 54 of track 50 is provided with an entrance ramp 56 andan exit ramp 58 by which vehicles (not shown) may enter and leave thetest track 50, respectively.

Second side 60 of track 50 has a downward inclined portion 62 of lengthL1. Downward incline 62 is preferably at an angle of about 5° to about10° to the horizontal, most preferably 6°, with length L1 preferablybeing about 30 feet.

The third side 66 of test track 50 is flat and horizontal.

The fourth side 70 of test track 50 preferably has an upwardly inclinedportion 72 of length L3. Preferably, the angle of incline 72 is fromabout 5° to about 10° from the horizontal, most preferably 6°.Preferably, length L3 is about 20 to 30 feet.

Preferably, a vehicle 28 (not shown) enters the first side 54 of testtrack 50 via entrance ramp 56 and moves along test track 50 in thedirection of the arrows in FIG. 5. Vehicle 28 is moved in decelerationmode, preferably at a constant negative rate of acceleration, over thedownwardly inclined portion 62, with the exhaust emissions of vehicle 28being tested at first test point 74 located at the lower end of inclinedportion 62.

The vehicle 28 preferably moves along the entire length of third side 66in a cruise mode, preferably at a constant velocity. The exhaustemissions of vehicle 28 are tested as it moves past the second testpoint 76 located on the third side 66 of test track 50.

On the fourth side 70 of test track 50, the vehicle is preferablyaccelerated in loaded mode at a constant rate of acceleration alongupwardly inclined portion 72. The exhaust emissions of vehicle 28 areagain tested at the third test point 78 located at the upper end ofinclined portion 72.

The vehicle 28 then proceeds along test track 50 back to the first side54. The vehicle exhaust may preferably be tested at fourth test point 80along first side 54, vehicle 28 moving in cruise mode, preferably at aconstant velocity, past test point 80. The vehicle can then either leavetest track 50 by exit ramp 58, which adjoins first side 54, or may makeanother circuit of test track 50.

At each of the test points 74, 76, 78 and 80 along test track 50 arelocated remote exhaust testers 14 comprising a source 16 and detector18. These testers 14 are shown as being identical to those describedabove in reference to FIG. 1, however the source 16 and detector 18 maybe on the same side of track 50 as shown in FIG. 2.

Although not shown in FIG. 5, a blower 20 such as that shown in FIG. 2is preferably positioned ahead of each test point 74, 76, 78 and 80 tobreak the exhaust plume with a curtain of air 45, a blower 20 beinglocated a sufficient distance ahead of each test point to allow theexhaust plume to reestablish itself at the test point.

As shown by FIG. 5, the three remote exhaust testers 16a, 16b and 16care each connected by wires 82 to a main console 84.

Console 84 is preferably provided with a processor (not shown) whichprocesses the test results, correlates the results of individual tests,and compares the exhaust emissions determined by the tests with apredetermined standard.

Each test result is preferably processed to determine firstly, whetheror not instantaneous values of velocity and acceleration of a vehiclemoving past a test point fall within predetermined ranges of velocityand acceleration; and secondly, whether or not average values ofvelocity and acceleration for movement of a vehicle over the entire testtrack, or any portion thereof, fall within predetermined ranges ofvelocity and acceleration.

If the velocity and/or acceleration are not within the predeterminedranges, then one or more test results may preferably be discarded. Onthe other hand, if the velocity and/or acceleration are withinpredetermined ranges, then the processor preferably calculates thevehicle's exhaust emissions based on the instantaneous and averagevelocity and acceleration of the vehicle.

Velocity and acceleration may preferably be measured by piezoelectricstrips, such as strips 43 shown in FIG. 2, located at specified pointsalong the test track, to determine the velocity and acceleration of thevehicle. Velocity may preferably be measured by determining the timerequired for one tire of the vehicle to pass over a strip 43, andacceleration may preferably be determined by measuring differences invelocity between a front and a rear tire of the vehicle.

The processor preferably generates a profile of the velocity andacceleration of the vehicle as it moves over the test track. Thisprofile shows whether or not movement of the vehicle is maintainedwithin predetermined ranges for average velocity and acceleration overany portion of the test track, and whether or not the instantaneousvelocity and acceleration of the vehicle at any test point is withinpredetermined ranges of instantaneous velocity and acceleration.

The results of individual tests may individually be compared against thepredetermined standard. Preferably, for the vehicle to pass theemissions test, at least two of the test results must meet thepredetermined standard.

Although the test results can be individually compared to thepredetermined standard, it is more preferred that the test results becorrelated to determine a composite level of emissions standards for thevehicle, this composite being compared against the predeterminedstandard. Preferably, a formula is utilized by the processor whichcombines test results obtained under different conditions of velocityand acceleration to obtain the composite emissions level for thevehicle.

In one preferred embodiment, the composite emissions level is theaverage of the emissions levels determined at each test point.

Although certain preferred methods for correlating test results andcomparing them to a predetermined standard have been described above, itis to be appreciated that specific methods of correlating and comparingtest results may be prescribed by government agencies in certainjurisdictions in which testing is carried out. Therefore, the processormay preferably be programmable so that it may be adapted for use indifferent jurisdictions requiring different methods of correlating andcomparing test results.

Although FIGS. 1 and 5 illustrate the test points being located atspecific locations along test tracks 12 and 50, it is to be understoodthat the positioning of the test points is variable.

Although test tracks 12 and 50 are shown as having inclined portions, itis to be appreciated that a test track according to the presentinvention could be designed which is substantially flat and horizontalthroughout its entire length. Vehicles would be driven along such atrack and tested at two or more test points under predeterminedconditions of velocity and acceleration. The velocity and accelerationof the vehicle would be substantially entirely controlled by the vehicledriver.

Although the invention has been described in connection with certainpreferred embodiments, it is not intended that it be limited thereto.Rather, it is intended that the invention cover all alternateembodiments as may be within the scope of the following claims.

I claim:
 1. A method of spectroscopic testing of exhaust emissions ofvehicles having internal combustion engines to estimate whether theemissions of any vehicle meet predetermined standards, comprising:movingeach said vehicle under its own power along a test track undercontrolled conditions of operation, said test track having an upwardlyinclined portion, a horizontal portion and a downwardly inclinedportion, the method comprising the steps of:(a) moving the vehicle toascend the upwardly inclined portion at a positive rate of accelerationand within a predetermined first range of velocities, and remotelytesting the exhaust emissions of the vehicle by spectroscopic means asthe vehicle ascends the upwardly inclined portion at a first test pointon the upwardly inclined portion; (b) moving the vehicle across thehorizontal portion at a substantially constant velocity and within apredetermined second range of velocities, and remotely testing theexhaust emissions of the vehicle by spectroscopic means as the vehiclecrosses the horizontal portion at a second test point on the horizontalportion; and (c) moving the vehicle to descend the downwardly inclinedportion at a negative rate of acceleration and within a predeterminedthird range of velocities, and remotely testing the exhaust emissions ofthe vehicle by spectroscopic means as the vehicle descends thedownwardly inclined portion at a third test point on the downwardlyinclined portion; comparing the test results from the first, second andthird test points of one vehicle with results for vehicles which meetthe predetermined standards, said steps (a), (b) and (c) being performedin any order.
 2. The method of claim 1, wherein step (a) is performedfirst, step (b) is performed second, and step (c) is performed third. 3.The method of claim 1, wherein:in step (a) the vehicle is operated in aloaded mode with an air:fuel ratio in the range of about 13.5:1 to about14.7:1; in step (b), the vehicle is operated in a cruise mode with anair:fuel ratio in the range of about 14.0:1 to about 15.0:1; and in step(c), the vehicle is operated in a deceleration mode with an air:fuelratio greater than the air:fuel ratio in the cruise mode.
 4. The methodof claim 3, wherein:in step (a) the vehicle is moved along the upwardlyinclined portion at a constant, positive rate of acceleration; and instep (c) the vehicle is moved along the downwardly inclined portion at aconstant, negative rate of acceleration.
 5. The method of claim 1,wherein:in step (a) the vehicle is moved along the upwardly inclinedportion at a constant, positive rate of acceleration; and in step (c)the vehicle is moved along the downwardly inclined portion at aconstant, negative rate of acceleration.
 6. The method of claim 1,wherein said inclined portions are inclined at an angle of about 2° toabout 10° relative to a horizontal reference plane and have a length ofabout 30 feet to about 100 feet, measured along the reference plane, andsaid horizontal portion has a length of about 40 to about 200 feet. 7.The method of claim 1, wherein a stream of air is directed at the trackahead of a test point, vehicles passing through said air stream beforemoving past said test point,said air stream clearing from the trackexhaust emissions carried along the track by a vehicle as said vehiclepasses through said air stream, the exhaust emissions tested at the testpoint substantially comprising only an exhaust plume emitted by exhaustpipe means of said vehicle between the air stream and the test point. 8.The method of claim 7, wherein a stream of air is directed at the trackahead of each test point.
 9. The method of claim 1, wherein said remotetesting is performed by remote sensing testing means located at eachtest point, comprising:a source of infrared radiation; and a detector ofinfrared radiation; said source emitting a beam of infrared radiationwhich passes through an exhaust plume of a vehicle, and is subsequentlyreceived by the detector, said exhaust plume located at the testingpoint and in close proximity to exhaust pipe means of a vehicle.
 10. Themethod of claim 1, wherein the velocity and acceleration of each saidvehicle are measured at said test points and at predetermined locationsalong said test track to determine whether or not the velocity andacceleration of each said vehicle fall within predetermined ranges ofvelocity and acceleration.
 11. A method of testing exhaust emissions ofvehicles having internal combustion engines, comprising:(a) a firstpre-screening step, comprising testing vehicles according to the methodof claim 1, to estimate whether the emissions of any vehicle meetpredetermined standards; and (b) a second step comprising testingexhaust emissions to accurately determine whether the emissions of anyvehicle meet predetermined standards, said second step not beingconducted for vehicles likely to have emissions meeting thepredetermined standard, as estimated by the pre-screening step.
 12. Themethod of claim 11, wherein said inclined portions are inclined at anangle of about 2° to about 10° relative to a horizontal reference planeand have a length of about 30 feet to about 100 feet, measured along thereference plane, and said horizontal portion has a length of about 40 toabout 200 feet.
 13. The method of claim 11, wherein said remote testingis performed by remote sensing testing means located at each test point,comprising:a source of infrared radiation; and a detector of infraredradiation; said source emitting a beam of infrared radiation whichpasses through an exhaust plume of a vehicle, and is subsequentlyreceived by the detector, said exhaust plume located at the testingpoint and in close proximity to exhaust pipe means of a vehicle.
 14. Themethod of claim 11, wherein the velocity and acceleration of each saidvehicle are measured at said test points and at predetermined locationsalong said test track to determine whether or not the velocity andacceleration of each said vehicle fall within predetermined ranges ofvelocity and acceleration.
 15. An apparatus for spectroscopic testing ofexhaust emissions of vehicles having internal combustion engines,comprising:(a) a test track over which vehicles are moved under theirown power under controlled conditions of operation, said test trackhaving an upwardly inclined portion, a horizontal portion and adownwardly inclined portion; (b) first remote sensing testing means fortesting the exhaust emissions of the vehicles by spectroscopic means,said first testing means located at a first test point on the upwardlyinclined portion, so as to test the vehicles in a first mode ofoperation; (c) second remote sensing testing means for testing theexhaust emissions of the vehicles by spectroscopic means, said secondtesting means located at a second test point on the horizontal portion,so as to test the vehicles in a second mode of operation; (d) thirdremote sensing testing means for testing the exhaust emissions of thevehicles by spectroscopic means, said third testing means located at athird test point on the downwardly inclined portion, so as to test thevehicles in third mode of operation; and (e) processing means forcomparing the test results from the first, second and third test pointsof one vehicle with results for vehicles which meet the predeterminedstandards.
 16. The apparatus of claim 15, further comprising:(f) blowermeans located ahead of a test point, said blower means blowing a streamof air directed at the track ahead of a test point, vehicles passingthrough said air stream before moving past said test point, said airstream clearing from the track exhaust emissions carried along the trackby a vehicle as said vehicle passes through said air stream, the exhaustemissions tested at the test point substantially comprising only anexhaust plume emitted by exhaust pipe means of said vehicle between theair stream and the test point.
 17. The apparatus of claim 16, whereinblower means are located ahead of each test point.
 18. The apparatus ofclaim 15, wherein said inclined portions are inclined at an angle ofabout 2° to about 10° relative to a horizontal reference plane and havea length of about 30 feet to about 100 feet, measured along thereference plane, and said horizontal portion has a length of about 40 toabout 200 feet.
 19. The apparatus of claim 15, wherein said remotesensing testing means located at each test point comprises:a source ofinfrared radiation and a detector of infrared radiation, said sourceemitting a beam of infrared radiation which passes through an exhaustplume of a vehicle and is subsequently received by the detector, saidexhaust plume located at the test point and in close proximity toexhaust pipe means of a vehicle.